Novel light sources such as light sources based on light emitting diodes (LEDs) or discharge lamps become increasingly more popular. Driver circuits for such light sources are operative to provide an output current or output voltage to a light-emitting means of the light source. The driver circuits may also be configured to perform additional functions, including control and/or communication functions. For illustration rather than limitation, communication between a driver circuit for a light source and a master unit may facilitate the implementation of automatic monitor procedures in which the correct operation of the light source is monitored by the master unit, automatic control of the light source by the master unit, and/or the implementation of feedback control loops in a lighting system having one or several light sources and which require the light source(s) to report data to the master unit.
Power line communication (PLC) is attractive because no separate, dedicated communication lines connected to the light source are required. PLC may be implemented in various forms. In some forms, PLC may be implemented as a one way communication. Supply interruptions and/or reversal of a direct current (DC) supply may be used to transmit data from a master to a slave. These techniques have the advantage of being inexpensive. However, the techniques may cause major disruption to the supply and may have severe limitations when it comes to individually addressing one of plural slaves connected to a same power line.
In other forms of PLC, a modulated signal is applied to a supply. Such techniques may also implement a two-way communication in which a slave can reply, sending communication back to the master. Conventionally, a dedicated PLC modulator is provided in the slave for modulating a signal onto the power line for communication towards the master. It is a considerable challenge to implement the PLC modulator of the slave in a cost-efficient manner. Power consumption caused by the PLC modulator may also be a concern. For illustration, a chipset which provides a receiver and transmitter may be used in the slave. The power dissipation of the transmitter and the power supply for the transmitter raise issues which must be addressed, e.g. by using dedicated componentry for supplying power to an amplifier of the transmitter and/or by providing dedicated heat sinks. This may add to the costs of the system, which is unattractive for many applications.